FIG. 1 is a schematic diagram of a space diversity system in the prior art. As shown in FIG. 1, a sending device includes only one transmit antenna in an enabled state, and the other transmit antenna is silent. However, for multiple receive antennas (using two receive antennas as an example in the figure) installed on a receiving device, each of the receive antennas can receive a signal sent by a transmit antenna that works, as long as a preset distance is satisfied in space. That is, the receiving device can simultaneously receive multiple received signals. Specifically, a signal sent by the transmit antenna shown in FIG. 1 is received by the two receive antennas of the receiving device through a transmission path 1 and a transmission path 2 respectively. That is, the obtained two received signals are the same. However, because there is no correlation between the transmission path 1 and the transmission path 2, the receiving device may combine the two received signals according to a rule, so that a reception gain can be increased for the signal sent by the transmit antenna.
However, it is found when signal receiving is performed by using the foregoing existing technology that, the foregoing signals transmitted through the transmission path 1 and the transmission path 2 are subject to interference from a communication environment in a transmission process, and quality of one signal may deteriorate. Therefore, signal-to-noise ratios of the two received signal differ relatively much from each other. In this case, if the two received signals are still combined, a combined signal not only cannot increase the reception gain but also has degraded quality, affecting subsequent signal processing.